The present invention relates generally to impulse radar guidance systems and methods, and more particularly, to an impulse radar guidance system and method for use with spinning guided projectiles.
Previous means to measure the roll angle of a projectile generally fall into one of three categories. The first is where the projectile is equipped with a roll gyroscope and a transmitter to communicate its roll angle to a launch control system. An example of this is an artillery round concept currently being developed by Bofors Weapons Systems of Sweden.
The second is where the projectile is provided with a polarizing reflector for use with either a radar or a laser. The polarization angle of received reflections indicates the roll angle. However, this method suffers from an ambiguity of 180xc2x0 in roll. Thus, half the time, the projectile will be commanded to deflect in the wrong direction.
The third is where the projectile is imaged with a fast camera shortly after launch to detennine its roll angle. Polarized reflections are used to count and keep track of subsequent rolls. This is a very complicated method which fails if the data stream is interrupted during flight of the projectile.
Accordingly, it is an objective of the present invention to provide for an improved guidance apparatus and method for use with guided projectiles that overcomes the limitations of the approaches outlined above. It is a further objective of the present invention to provide for an impulse radar guidance apparatus and method for use with a spinning guided projectile has been disclosed that uses an asymmetric waveform to determine the instantaneous roll angle of the spinning projectile and resolves the 180xc2x0 roll ambiguity of the projectile.
To meet the above and other objectives, the present invention provides for an improved impulse radar guidance system and method for use with spinning projectiles. The present invention provides for a method and apparatus for tracking the flight of a spinning projectile, bullet, missile, or artillery shell, for example, using an all-weather radar. By means of a novel impulse waveform and reflector on the spinning projectile, an impulse radar (tracker) measures the instantaneous roll angle of the spinning projectile during its flight. The projectile has a maneuvering. device, such as a side-firing thruster, and a receiver that is used as a data link to receive commands. Terminal maneuvering of the spinning projectile is accomplished by commanding the maneuvering device or thruster to fire at one or more specific roll-angles to deflect the flight direction of the projectile at a target.
The purpose of the present invention is to provide an all-weather long-range control system for spinning command-guided projectiles. Such projectiles can be very low cost, since they do not require seekers or complex on-board computers. Furthermore, a spinning projectile needs only a single deflection thruster to maneuver in any direction since the thruster can be fired at appropriate roll angles. In many applications, the thruster need be fired only once (a single-shot thruster) late in the flight in order to correct for initial launch errors.
The present invention thus provides a simple radar-means to measure the roll angle of the projectile at any time during its flight. The present invention may be used to provide an all-weather guided-bullet upgrade for the Phalanx gun system in the inventory of the U.S. Army.
The present invention provides for an improvement over the Bofors artillery-round concept outlined in the Background section. The present invention is simpler, lower in cost, and is believed to be more accurate. The present invention makes possible artillery rounds having much less dispersion in their impact patterns and thus makes them more effective than conventional systems.
The present invention makes possible, the development of very small guided-bullet systems which may be used for self defense against incoming missile threats. Applications range from defense of ground vehicles to aircraft self-defense.